Demand for wireless broadband access communication is trending upwards. Such systems include Local Area Network (LAN) systems and Metropolitan Area Network (MAN) systems, for example. Although new wireless systems are continually being developed, such as IEEE 802.16 wireless broadband communication systems, the amount of frequency spectrum is limited within each system while demands for increased Quality of Service (QoS) increase. As a result, more and more users are driven to use a fixed amount of bandwidth with a given quality level in any particular broadband system. This results in congestion and subsequently problems in communication latency in obtaining a communication link when entering the system. This problem is compounded for mobile communication systems, wherein a mobile station moving between cells of a broadband system will require communication overhead to deal with handovers between base stations, resulting in even further delay or latency issues.
Specifically, during handover conditions in IEEE 802.16 communication systems a Mobile Station (MS) exchanges a number of Media Access Control (MAC) Management Messages with a Base Station (BS). These messages form a series of Request/Response pairs, i.e. the MS receives a downlink message and, as a result, generates a response message in the uplink direction. Alternatively, the BS receives an uplink message and, as a result, generates a response message in the downlink direction. Decisions regarding handover procedures are made and communicated between an MS connected with a BS in time segments called frames. The size of a frame in IEEE 802.16 is variable and can range from two to twenty milliseconds.
One of the factors that can significantly affect the delay associated with a communication link handover is the time at which channel descriptor data about the BSs in an 812.16 network is provided to the MS. Currently, there exists no means for the MS to have the most recent identifying channel descriptor data of a target BS available in a handover procedure so that the MS is quickly informed of data such as uplink channel descriptors (UCD) and downlink channel descriptors (DCD) to avoid delaying the handover procedures. Without informing the MS of the identifying data of the target BS in a timely manner, the MS must wait until a serving BS notifies the MS of the target BS identifying data at the low frequency of approximately once a second as required by IEEE 802.16 standards. Alternatively, the MS has to first switch to the target BS and wait for the target BS to broadcast its own identifying data, which further increases delay.
Referring to FIG. 2, which is described in more detail below, the procedure of handing over the MS from the serving BS to the target BS is shown as currently enabled by the IEEE 802.16 standard. As seen, there is no requirement during the handover process to inform the MS of the most recent identifying data before the handover actually occurs. At any time during the process, the target BS identifying data, including the UCD and DCD, can be sent to the MS and the identifying data can change. The MS might not have the correct data to accurately complete the handover procedure if the UCD and DCD change between the time the last identifying message is sent to the MS and the time the handover is initiated. In any event, the MS must wait for the synchronization between the MS and the target BS before it will know the identifying data and, in particular, the correct UCD and DCD of the target BS. Alternatively, the MS has to switch to the target BS first and then wait for that BS to broadcast its own identifying data and in particular the correct UCD and DCD.
Therefore, a need exists for a method and apparatus that reduces the amount of latency and delay in wireless broadband communication systems, particularly in communication handover procedures. It would also be an advantage to inform MS of the UCD and DCD of the target MS in a timely manner and before the process of handing over the MS from the serving BS to the target BS occurs. Such an improvement would provide the MS with more accurate and current data to increase the speed of the handover process.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.